Ground cover, photosynthetic rate and tuber yield of potato (Solanum tuberosum L.) crops from seed tubers with different physiological age modified by foliar applications of plant growth regulators

Summary The modifying effects of applying the plant growth regulators (PGRs) benzylaminopurine (BAP), gibberellic acid (GA₃) and BAP+GA₃ on physiological age were studied. Two experiments with two cultivars, differing in rate of physiological ageing (medium-early Pampeana, medium-late Huinkul) and two storage systems were performed during 1988/89 and 1989/90 in two different potato areas of Argentina. In both seasons seed tubers stored in heaps reached an advanced physiological age at planting, compared with tubers from the cold store. Seed tubers of cv. Pampeana were older than those of Huinkul. compared with control crops, those sprayed with BAP maintained ground cover and photosynthesis for longer, and those sprayed with GA₃ for a shorter period. Consequently tuber yield was decreased by GA₃ in 1988/89, but in 1989/90 all crops treated with PGRs outyielded the control. BAP could overcome effects of advanced physiological age on crop senescence and tuber yield. CIC BA This work was carried out with a research grant from CAFPTA (249/89).     

Use of soil solarization to improve growth of eucalyptus forest nursery seedlings in Argentina

Damping-off and root rot are major diseases affectingseedlings of Eucalyptus species in forestnurseries in temperate regions in Argentina. The mostcommon fungi associated with these diseases andaffecting the vigor of the root system are Fusarium and Pythium species. Two forestnursery experiments were conducted in the province ofBuenos Aires, Argentina, to determine the effect ofsoil solarization on growth of Eucalyptusviminalis seedlings and relate this effect to thepresence of pathogenic and native ectomycorrhizaepopulations in roots and nutrient availability insoil. Changes in populations of soilborne pathogenswere determined by a bioassay that relates theirpotential to induce disease. Changes in nativeectomycorrhizae were assesed by measuring colonizationlevels in roots. Nutrient availability was determinedby the amount of nitrates released by solarization.Solar heating decreased pathogenic and ectomycorrhizalinoculum potential and increased soil nitrates.Seedling growth in solarized seedbeds may be relatedto a low initial pathogenic population and/or toincreases in nitrate availability. Solarization mayinduce soil suppressiveness against re-establishmentof major seedling pathogens in treated soils.